Modern day warming drawers typically use low power, low cost “calrod” sheathed tubular heating elements to warm the drawer cavity, inexpensive glass or ceramic wool insulation to reduce heat flow out of the drawer cabinet, and low cost gas-bulb expansion thermostats to regulate drawer cavity temperature. Often, the electrical power of the “calrods” is set to just balance the losses of the warming drawer at maximum requested temperature, thereby allowing operation at a safe temperature in the event the drawer thermostat fails in an electrically conductive mode.
Because of the high thermal lag of the “calrod”, because of the characteristic low cost and low performance of typical insulations, and because of the need to keep design element and electronic control component count down, current technology warming drawers fail to meet consumer expectations in a number of respects.
For example, current technology warming drawers require a 20 minute time period for preheating to user selected temperature and, thus, the consumer must wait. Also, when an article is placed into a current technology warming drawer, the drawer temperature is momentarily changed to kitchen temperature and the thermal mass of the typical calrod causes very slow recovery. Thus, the warming drawer is slow to recover from drawer loading and unloading temperature changes.
Moreover, due to the use of low cost insulation, standby energy loss of typical warming drawers has been measured to be as high as 50%. Such a standby energy loss is very high. Additionally, because the calrod systems of current technology warming drawers are typically low power and low temperature radiant, free convection systems, stacks of dinner plates, cups and saucers, or other thick items are heated only unidirectionally. Thus, these warming drawers have low drawer temperature uniformity such that heat transfer to the entire volume of the article being heated is limited.
Finally, drawer slide systems typically used in current technology warming drawers are of poor quality. At full extension of the drawer slide systems, the drawers “wobble” from side to side, which detracts from the stability, safety, usefulness, and user perception of quality of the warming drawers.